Electric switches in buckle for safety belt are required in order to indicate the use condition of the safety belt (i.e. fastened or unfastened). They are operated on insertion of the insert tongue and then produce a signal, which is supplied via a cable, extending out of the casing of the buckle, to a control system. Dependent on the type of control system, different forms of switch are required. For a belt warning system it is possible to employ a normally closed or a normally open switch. For a belt warning system in combination with a belt handling device as an electric switch a change over switch is required. Finally, for an air bag inquiry system a normally closed or a normally open switch is required with two different electrical resistors. The installation of such electric switches with the associated connecting cables is presently performed in the course of the assembly of the buckle. The casing of the buckle is made in two parts and is put together only after fitting of the electric switch or switches on the housing. Such a two-part housing not only involves more complex assembly than a single-piece casing, it is also less strong mechanically and less able to prevent the ingress of dirt. While assembly of a buckle without electric switches is substantially automated, the fitting thereof with various different switch systems renders necessary separate assembly and checking steps. Moreover, handling during assembly is hindered by the presence of already existing switches with their connecting cables.